Heat exchanger and air conditioner

ABSTRACT

A fin of a heat exchanger includes: a plurality of intermediate plates arranged one above another and dividing a space between adjacent ones of flat tubes into air passages; a plurality of tube insertion portions each provided between vertically adjacent ones of the intermediate plates, with an upwind side thereof being open such that a corresponding one of the flat tubes is inserted therein; a vertically extending downwind plate that is continuous with downwind ends of the plurality of intermediate plates arranged one above another; and a plurality of upwind plates extending further toward an upwind side than the flat tubes from upwind side ends of the intermediate plates. Each of the upwind plates is provided with at least one upwind side heat-transfer portion which projects toward the air passages.

TECHNICAL FIELD

The present invention relates to heat exchangers having a flat tube and a fin and configured to exchange heat between a fluid flowing in the flat tube and air, and air conditioners having the heat exchangers.

BACKGROUND ART

Heat exchangers having a flat tube and a fin have been known. Patent Document 1 and Patent Document 2 show heat exchangers of this type. In the heat exchangers shown in these patent documents, a plurality of flat tubes, each extending in a horizontal direction, are arranged one above another with a predetermined space between the flat tubes, and plate-like fins are arranged in a direction along which the flat tubes extend, with a predetermined space between the fins. For example, in the heat exchanger shown in FIG. 2 of Patent Document 2, elongated cutouts are formed in the fins, and the flat tube is inserted in each of the cutouts. In this heat exchanger, air flowing in an air passage between adjacent flat tubes is heat exchanged with a fluid flowing in the flat tube.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Publication No. 2003-262485 -   Patent Document 2: Japanese Patent Publication No. 2010-054060

SUMMARY OF THE INVENTION Technical Problem

In the heat exchanges shown in Patent Documents 1 and 2, when the air flowing in the air passage is 0° C. or lower, moisture in the air freezes and frost may adhere to the surfaces of the fins. If the amount of frost adhering to the surfaces of the fins increases in the air passage, a heat-transfer rate of the fin may decrease, or a flow pass resistance of the air passage may increase.

The present invention is thus intended to prevent frost, in a heat exchanger having a plurality of flat tubes and a plurality of fins, from adhering to a surface of each fin in an air passage.

Solution to the Problem

The first aspect of the present invention is directed to a heat exchanger, including: a plurality of flat tubes (33) arranged one above another such that flat surfaces thereof face each other; and a plurality of vertically extending, plate-like fins (36) arranged in an extension direction of the flat tubes (33), wherein each of the fins (36) includes a plurality of intermediate plates (70) arranged one above another and dividing a space between adjacent ones of the flat tubes (33) into air passages (40), a plurality of tube insertion portions (46) each provided between vertically adjacent ones of the intermediate plates (70), with an upwind side thereof being open such that a corresponding one of the flat tubes (33) is inserted therein, a vertically extending downwind plate (75) that is continuous with downwind ends of the plurality of intermediate plates (70) arranged one above another, and a plurality of upwind plates (77) extending further toward an upwind side than the flat tubes (33) from upwind side ends of the intermediate plates (70), and each of the upwind plates (77) is provided with at least one upwind side heat-transfer portion (81, 91, 92, 95) which projects in a thickness direction of the fins (36).

In the fin (36) of the first aspect of the present invention, a plurality of upwind plates (77) project from the upwind ends of the plurality of intermediate plates (70) to the upwind side. When air passes through the heat exchanger serving as an evaporator, the air is cooled first by the upwind plates (77). When the air is cooled by the upwind plates (77) to a temperature equal to or lower than a dew point, moisture in the air is condensed. When the temperature of the air flowing on the lateral sides of the upwind plates (77) is equal to or lower than 0° C., moisture in the air turns into frost on the surface of the upwind plates (77). In the present invention, since moisture in the air flowing on the lateral sides of the upwind plates (77) is condensed, or turns into frost as described above, the air is dehumidified.

The air dehumidified in this manner flows in the air passages (40) along the intermediate plates (70). The intermediate plates (70) are located relatively close to the flat tubes (33), and thus, the air flowing in the air passages (40) is cooled rapidly. However, this air has been dehumidified by the upwind plates (77), and therefore, the accumulation of frost on the surfaces of the intermediate plate (70) is reduced.

Here, the air flowing on the lateral sides of the upwind plates (77) is not easily cooled, compared to the air flowing in the air passages (40), because the upwind plates (77) are located relatively far from the flat tubes (33). However, in the fin (36) of the present invention, each of the upwind plates (77) is provided with an upwind side heat-transfer portion (81, 91, 92, 95), and therefore, heat transfer between the air and the upwind plates (77) is promoted. As a result, the air flowing on the lateral sides of the upwind plates (77) can be easily cooled, and the effect of dehumidifying the air is improved. Thus, in the present invention, the accumulation of frost on the surfaces of the intermediate plates (70) can be further advantageously reduced.

The second aspect of the present invention is that in the first aspect of the present invention, the upwind side heat-transfer portion includes a rib (91, 92) which extends in a protruding direction of the upwind plates (77).

According to the second aspect of the present invention, the upwind plate (77) is provided with the rib (91, 92). The rib (91, 92) comprises an upwind side heat-transfer portion. Thus, the air flowing on the lateral sides of the upwind plates (77) can be easily cooled, and the effect of dehumidifying the air is improved.

Further, in the fin (36) of the present invention, the upwind plate (77) projects from the intermediate plate (70). This may lead to easy bending of the upwind plate (77) in a horizontal direction with respect to the intermediate plate (70). However, the rib (91, 92) of the upwind plate (77) is provided so as to extend in the projecting direction of the upwind plate (77) to increase the bending strength of the upwind plate (77) in the horizontal direction. Thus, it is possible to prevent the upwind plate (77) from being bent in the horizontal direction.

The third aspect of the present invention is that in the second aspect of the present invention, the upwind side heat-transfer portion includes an intermediate heat-transfer portion (81, 95) provided at a middle portion, in a vertical direction, of each of the upwind plates (77), and the rib (91, 92) provided on at least one of an upper side or a low side of the intermediate heat-transfer portion (81, 95).

According to the third aspect of the present invention, the upwind plate (77) is provided with the intermediate heat-transfer portion (81, 95). The intermediate heat-transfer portion (81, 95) comprises an upwind side heat-transfer portion. Since the intermediate heat-transfer portion (81, 95) is provided at a middle portion, in the vertical direction, of the upwind plate (77), heat transfer between the air and the intermediate heat-transfer portion (81, 95) is promoted, and the effect of cooling the air is improved. The intermediate heat-transfer portion (81, 95) provided on the upwind plate (77) may easily lead the air to the upper side or the lower side of the intermediate heat-transfer portion (81, 95). However, in the present invention, the rib (91, 92) is provided on the upper side or the lower side of the intermediate heat-transfer portion (81, 95), and therefore, heat transfer between the air and the rib (91, 92) is promoted as well. As a result, the effect of cooling the air flowing on the lateral sides of the upwind plates (77) is further improved.

The fourth aspect of the present invention is that in any one of the first to third aspects of the present invention, the upwind side heat-transfer portion includes a protrusion (81) which extends in a direction orthogonal to an air passage direction.

According to the fourth aspect of the present invention, the upwind plate (77) is provided with the protrusion (81). The protrusion (81) comprises an upwind side heat-transfer portion. Since the protrusion (81) extends in a direction which intersects with the air passage direction, heat transfer between the air and the protrusion (81) is promoted, and the effect of cooling the air is improved.

The fifth aspect of the present invention is that in any one of the first to fourth aspects of the present invention, the upwind side heat-transfer portion includes a raised portion (95) formed by cutting and bending part of the fin (36).

According to the fifth aspect of the present invention, the upwind plate (77) is provided with the raised portion (95) as an upwind side heat-transfer portion. As a result, heat transfer between the air and the raised portion (95) is promoted, and the effect of cooling the air is improved.

The sixth aspect of the present invention is directed to an air conditioner, and having a refrigerant circuit (20) including the heat exchanger (30) of any one of the first to fifth aspects of the present invention, wherein the refrigerant circuit (20) performs a refrigeration cycle by circulating a refrigerant.

According to the sixth aspect of the present invention, the heat exchanger (30) of the first to fifth aspects of the present invention is applied to the air conditioner. Thus, in the heat exchanger (30) serving as an evaporator, the accumulation of frost on the surfaces of the intermediate plates (70) which partition the air passages (40) is reduced.

Advantages of the Invention

In the present invention, the upwind plates (77) are provided so as to extend from the intermediate plates (70) of the fin (36) to the upwind side, and each of the upwind plates (77) is provided with the upwind side heat-transfer portion (81, 91, 92, 95). Thus, the air before flowing into the air passages (40) can be dehumidified by the upwind plates (77). This can reduce the accumulation of frost on the surfaces of the intermediate plates (70), and thus, it is possible to prevent a reduction in heat-transfer rate of the fin (36), and an increase in flow pass resistance of the air passages (40).

According to the second aspect of the present invention, the rib (91, 92) can improve the effect of cooling the air, and prevent bending of the upwind plates (77). Since leaning of the upwind plates (77) is prevented as mentioned, the air can flow evenly into the air passages (40). As a result, reliability of the heat exchanger can be ensured.

According to the third to fifth aspects of the present invention, heat transfer between the air and the upwind plates (77) can be promoted, and the effect of cooling the air by the upwind plates (77) can be further improved. Further, according to the fifth aspect of the present invention, the tip of the raised portion (95) is in contact with the adjacent upwind plate (77), thereby preventing the upwind plate (77) from leaning horizontally.

According to the sixth aspect of the present invention, in the heat exchanger (30) serving as an evaporator, the amount of frost adhering to the intermediate plates (70) facing the air passages (40) can be reduced. Thus, it is possible to reduce the time of the defrosting operation of the heat exchanger (30) for melting the frost, and accordingly extend the time of the heating operation by the reduced period of time. As a result, it is possible to promote energy conservation of the air conditioner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram showing a schematic configuration of an air conditioner having a heat exchanger of an embodiment.

FIG. 2 is an oblique view schematically showing the heat exchanger of the embodiment.

FIG. 3 is a partial cross-sectional view of the front side of the heat exchanger of the embodiment.

FIG. 4 is a cross-sectional view of part of the heat exchanger taken along the line A-A of FIG. 3.

FIG. 5 shows a main part of a fin of the heat exchanger of the embodiment. FIG. 5(A) is a front side of the fin. FIG. 5(B) is a cross-sectional view taken along the line B-B of FIG. 5(A).

FIG. 6 shows cross-sectional views of the fins of the heat exchanger of the embodiment. FIG. 6(A) is a cross-section taken along the line C-C of FIG. 5. FIG. 6(B) is a cross-section taken along the line D-D of FIG. 5.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described in detail below, based on the drawings. The following embodiment is merely a preferred example in nature, and is not intended to limit the scope, applications, and use of the invention.

A heat exchanger (30) of the embodiment comprises an outdoor heat exchanger (23) of an air conditioner (10) described later.

—Air Conditioner—

The air conditioner (10) having the heat exchanger (30) of the present embodiment will be described with reference to FIG. 1.

<Configuration of Air Conditioner>

The air conditioner (10) has an outdoor unit (11) and an indoor unit (12). The outdoor unit (11) and the indoor unit (12) are connected to each other via a liquid communication pipe (13) and a gas communication pipe (14). In the air conditioner (10), a refrigerant circuit (20) is formed by the outdoor unit (11), the indoor unit (12), the liquid communication pipe (13), and the gas communication pipe (14).

The refrigerant circuit (20) includes a compressor (21), a four-way valve (22), an outdoor heat exchanger (23), an expansion valve (24), and an indoor heat exchanger (25). The compressor (21), the four-way valve (22), the outdoor heat exchanger (23), and the expansion valve (24) are accommodated in the outdoor unit (11). The outdoor unit (11) is provided with an outdoor fan (15) configured to supply outdoor air to the outdoor heat exchanger (23). The indoor heat exchanger (25) is accommodated in the indoor unit (12). The indoor unit (12) is provided with an indoor fan (16) configured to supply indoor air to the indoor heat exchanger (25).

The refrigerant circuit (20) is a closed circuit filled with a refrigerant. In the refrigerant circuit (20), a discharge side of the compressor (21) is connected to a first port of the four-way valve (22), and a suction side of the compressor (21) is connected to a second port of the four-way valve (22). In the refrigerant circuit (20), the outdoor heat exchanger (23), the expansion valve (24), and the indoor heat exchanger (25) are provided sequentially from a third port to a fourth port of the four-way valve (22).

The compressor (21) is a scroll type or rotary type hermetic compressor. The four-way valve (22) switches between a first state (the state shown in broken line in FIG. 1) in which the first port communicates with the third port, and the second port communicates with the fourth port, and a second state (the state shown in solid line in FIG. 1) in which the first port communicates with the fourth port, and the second port communicates with the third port. The expansion valve (24) is a so-called electronic expansion valve (24).

In the outdoor heat exchanger (23), the outdoor air is heat exchanged with the refrigerant. The outdoor heat exchanger (23) is comprised of the heat exchanger (30) of the present embodiment. In the indoor heat exchanger (25), the indoor air is heat exchanged with the refrigerant. The indoor heat exchanger (25) is comprised of a so-called cross-fin type fin-and-tube heat exchanger having a circular heat-transfer tube.

<Cooling Operation>

The air conditioner (10) performs a cooling operation. The four-way valve (22) is set to the first state during the cooling operation. The outdoor fan (15) and the indoor fan (16) are driven during the cooling operation.

The refrigerant circuit (20) performs a refrigeration cycle. Specifically, the refrigerant discharged from the compressor (21) passes through the four-way valve (22), flows into the outdoor heat exchanger (23), and dissipates heat to the outdoor air and condenses. The refrigerant flowing out of the outdoor heat exchanger (23) expands when it passes through the expansion valve (24), flows into the indoor heat exchanger (25), and takes heat from the indoor air and evaporates. The refrigerant flowing out of the indoor heat exchanger (25) passes through the four-way valve (22) and is then sucked into the compressor (21) and compressed. The indoor unit (12) supplies air which has been cooled in the indoor heat exchanger (25) to an indoor space.

<Heating Operation>

The air conditioner (10) performs a heating operation. The four-way valve (22) is set to the second state during the heating operation. The outdoor fan (15) and the indoor fan (16) are driven during the heating operation.

The refrigerant circuit (20) performs a refrigeration cycle. Specifically, the refrigerant discharged from the compressor (21) passes the four-way valve (22), flows into the indoor heat exchanger (25), and dissipates heat to the indoor air and condenses. The refrigerant flowing out of the indoor heat exchanger (25) expands when it passes through the expansion valve (24), flows into the outdoor heat exchanger (23), and takes heat from the outdoor air and evaporates. The refrigerant flowing out of the outdoor heat exchanger (23) passes through the four-way valve (22) and is then sucked into the compressor (21) and compressed. The indoor unit (12) supplies air which has been heated in the indoor heat exchanger (25) to an indoor space.

<Defrosting Operation>

As described above, the outdoor heat exchanger (23) functions as an evaporator in the heating operation. In the operation under low outdoor air temperature conditions, the evaporation temperature of the refrigerant in the outdoor heat exchanger (23) may sometimes be below 0° C. In this case, the moisture in the outdoor air turns into frost and adheres to the outdoor heat exchanger (23). To avoid this, the air conditioner (10) performs a defrosting operation every time a duration of the heating operation reaches a predetermined value (e.g., several tens of minutes), for example.

To start the defrosting operation, the four-way valve (22) is switched from the second state to the first state, and the outdoor fan (15) and the indoor fan (16) are stopped. In the refrigerant circuit (20) during the defrosting operation, a high temperature refrigerant discharged from the compressor (21) is supplied to the outdoor heat exchanger (23). The frost adhering to the surface of the outdoor heat exchanger (23) is heated and melted by the refrigerant. The refrigerant which dissipates heat in the outdoor heat exchanger (23) sequentially passes through the expansion valve (24) and the indoor heat exchanger (25), and is then sucked into the compressor (21) and compressed. When the defrosting operation is finished, the heating operation starts again. That is, the four-way valve (22) is switched from the first state to the second state, and the outdoor fan (15) and the indoor fan (16) are driven again.

—Heat Exchanger of First Embodiment—

The heat exchanger (30) of the present embodiment which comprises the outdoor heat exchanger (23) of the air conditioner (10) will be described with reference to FIGS. 2 to 6.

<General Configuration of Heat Exchanger>

As shown in FIG. 2 and FIG. 3, the heat exchanger (30) of the present embodiment includes one first header collecting pipe (31), one second header collecting pipe (32), a plurality of flat tubes (33), and a plurality of fins (35). The first header collecting pipe (31), the second header collecting pipe (32), the flat tubes (33), and the fins (35) are all aluminum alloy members, and are attached to one another with solder.

Both of the first header collecting pipe (31) and the second header collecting pipe (32) are in an elongated hollow cylindrical shape, with both ends closed. In FIG. 3, the first header collecting pipe (31) is provided upright at the left end of the heat exchanger (30), and the second header collecting pipe (32) is provided upright at the right end of the heat exchanger (30). In other words, the first header collecting pipe (31) and the second header collecting pipe (32) are provided such that their axial directions are vertical.

As is also shown in FIG. 4, the flat tube (33) is a heat-transfer tube having a flat oblong cross section or a rectangular cross section with rounded corners. In the heat exchanger (30), the plurality of flat tubes (33) extend in a horizontal direction, and are arranged such that the flat surfaces thereof face each other. Further, the plurality of flat tubes (33) are arranged one above another with a predetermined space between the flat tubes (33). One end of each of the flat tubes (33) is inserted in the first header collecting pipe (31), and the other end of the flat tube (33) is inserted in the second header collecting pipe (32).

Each fin (36) is in a plate-like shape, and the fins (36) are arranged in an extension direction of the flat tube (33) with a predetermined space between the fins (36). In other words, the fins (36) are arranged to be substantially orthogonal to the extension direction of the flat tube (33). As will be described in detail later, an area of each fin (36) which is located between vertically adjacent flat tubes (33) comprises an intermediate plate (70).

As shown in FIG. 3, in the heat exchanger (30), a space between vertically adjacent flat tubes (33) is divided into a plurality of air passages (40) by the intermediate plates (70) of the fins (36). In the heat exchanger (30), the refrigerant flowing in the fluid passages (34) of the flat tube (33) exchanges heat with the air flowing in the air passages (40).

<Configuration of Fin>

As shown in FIG. 4 and FIG. 5, each of the fins (36) is a vertically elongate plate-like fin formed by pressing a metal plate. The thickness of each fin (36) is approximately 0.1 mm.

The fin (36) is provided with a plurality of elongate cutouts (45) each extending in a width direction (i.e., in an air passage direction) of the fin (36) from a leading edge (38) of the fin (36). The plurality of cutouts (45) are formed in the fin (36) at predetermined intervals in a longitudinal direction (i.e., a vertical direction) of the fin (36). Of the cutout (45), a portion between the intermediate plates (70) of the fins (36) comprises a tube insertion portion (46). The flat tube (33) is inserted in the tube insertion portion (46) from the open upwind side, and is held. The width of the tube insertion portion (46) in the vertical direction is substantially equal to the width of the thickness of the flat tube (33), and the length of the tube insertion portion (46) is substantially equal to the width of the flat tube (33).

The flat tube (33) is inserted in the tube insertion portion (46) of the fin (36) from the leading edge (38) of the fin (36). The flat tube (33) is attached to the periphery of the tube insertion portion (46) with solder. That is, the flat tube (33) is fitted to the periphery of the tube insertion portion (46) which is part of the cutout (45).

The fin (36) includes a plurality of intermediate plates (70) in areas between vertically adjacent flat tubes (33), a downwind plate (75) provided on the downwind side of the intermediate plates (70), and an upwind plate (77) provided on the upwind side of each of the plurality of intermediate plates (70). The intermediate plates (70) divide the space between vertically adjacent flat tubes (33) into the air passages (40). That is, the intermediate plates (70) face the air passages (40). The downwind plate (75) is continuous with the downwind ends of all the intermediate plates (70) arranged one above another. Each of the upwind plate (77) projects from a middle portion in the vertical direction of the upwind end of each intermediate plate (70) toward the upwind side. The height of each upwind plate (77) is smaller than the height of each intermediate plate (70), and the width of the upwind plate (77) is narrower than the width of the intermediate plate (70).

The fin (36) is provided with louvers (50 a, 50 b) and protrusions (81-83). In the fin (36), the protrusions (81-83) are located upwind of the louvers (50 a, 50 b). The numbers of the protrusions (81-83) and the louvers (50 a, 50 b) described below are merely examples.

Specifically, the fin (36) is provided with three protrusions (81-83) in an upwind side area. The three protrusions (81-83) are arranged side by side in the air passage direction (i.e., the direction from the leading edge (38) to the trailing edge (39) of the fin (36)). That is, the fin (36) is provided with a first protrusion (81), a second protrusion (82), and a third protrusion (83) sequentially from the upwind side to the downwind side. In the fin (36), the first protrusion (81) lies across the upwind plate (77) and the intermediate plate (70), and the second protrusion (82) and the third protrusion (83) are provided on the intermediate plate (70).

Each of the protrusions (81-83) has an inverted V shape formed by making the fin (36) protrude toward the air passage (40). The three protrusions (81-83) protrude to the same direction. In the fin (36) of the present embodiment, the protrusions (81-83) protrude to the right when viewed from the leading edge (38) of the fin (36). Ridges (81 a, 82 a, 83 a) of the protrusions (81-83) (i.e., the line on the tip of each protrusion in the inverted V shape) are substantially in parallel with the leading edge (38) of the fin (36). That is, the ridges (81 a, 82 a, 83 a) of the protrusions (81-83) intersect with the airflow direction in the air passage (40).

As shown in FIG. 5(B), the height H1 of the first protrusion (81) in the protrusion direction, the height H2 of the second protrusion (82) in the protrusion direction, and the height H3 of the third protrusion (83) in the protrusion direction are equal (H1=H2=H3). As shown in FIG. 5(A), the width W1 of the first protrusion (81) in the air passage direction is smaller than the width W2 of the second protrusion (82) in the air passage direction, and the width W3 of the third protrusion (83) is smaller than the width W1 of the first protrusion (81) in the air passage direction (W1<W2<W3).

The intermediate plate (70) of the fin (36) is provided with a group of louvers (50 a, 50 b) at the downwind side of the protrusions (81-83). The louvers (50 a, 50 b) are obtained by giving a plurality of slit-like cuts in the intermediate plate (70) and plastically deforming a portion between adjacent cuts as if twisting the portion. The longitudinal direction of each louver (50 a, 50 b) is substantially parallel to the leading edge (38) of the fin (36) (i.e., the vertical direction). That is, the longitudinal direction of each louver (50 a, 50 b) intersects with the air passage direction. The lengths of the louvers (50 a, 50 b) are equal to each other.

As shown in FIG. 5(B), the louvers (50 a, 50 b) are tilted with respect to their peripheral flat portions. Specifically, bent-out ends (53 a, 53 b) on the upwind side of the louvers (50 a, 50 b) protrude to the left when viewed from the leading edge (38) of the fin (36). On the other hand, bent-out ends (53 a, 53 b) of the louvers (50 a, 50 b) on the downwind side protrude to the right when viewed from the leading edge (38) of the fin (36).

As shown in FIGS. 6(A) and 6(B), each of the bent-out ends (53 a, 53 b) of the louvers (50 a, 50 b) includes a main edge (54 a, 54 b), an upper edge (55 a, 55 b), a lower edge (56 a, 56 b). The main edge (54 a, 54 b) extends substantially in parallel with the leading edge (38) of the fin (36). The upper edge (55 a, 55 b) extends from the upper end of the main edge (54 a, 54 b) to the upper end of the louver (50 a, 50 b), and is tilted with respect to the main edge (54 a, 54 b). The lower edge (56 a, 56 b) extends from the lower end of the main edge (54 a, 54 b) to the lower end of the louver (50 a, 50 b), and is tilted relative to the main edge (54 a, 54 b).

As shown in FIG. 5(A) and FIG. 6(A), in each of the plurality of louvers (50 a) located on the upwind side, a tilt angle θ2 of the lower edge (56 a) with respect to the main edge (54 a) is smaller than a tilt angle θ1 of the upper edge (55 a) with respect to the main edge (54 a) (i.e., θ2<θ1). Thus, in each louver (50 a), the lower edge (56 a) is longer than the upper edge (55 a). The upwind side louver (50 a) is an asymmetric louver in which the shape of the bent-out end (53 a) is asymmetric in the vertical direction.

On the other hand, as shown in FIG. 5(A) and FIG. 6(B), in each of the plurality of louvers (50 b) located on the downwind side, a tilt angle θ4 of the lower edge (56 b) with respect to the main edge (54 b) is equal to a tilt angle θ3 of the upper edge (55 b) with respect to the main edge (54 b) (i.e., θ4=θ3). The louver (50 b) is a symmetric louver in which the shape of the bent-out end (53 b) is symmetric in the vertical direction. The tilt angle θ3 of the upper edge (55 b) of the downwind side louver (50 b) is equal to the tilt angle θ1 of the upper edge (55 a) of the upwind side louver (50 a) (i.e., θ3=θ1).

As shown in FIG. 5(A), the length L1 from the upper ends of the second protrusion (82) and the third protrusion (83) to the upper end of the intermediate plate (70), the length L2 from the lower ends of the second protrusion (82) and the third protrusion (83) to the lower end of the intermediate plate (70), the length L3 from the upper ends of the louvers (50 a, 50 b) to the upper end of the intermediate plate (70), and the length L4 from the lower ends of the louvers (50 a, 50 b) to the lower end of the intermediate plate (70) are the same.

In each fin (36), one auxiliary protrusion (85) lies across the intermediate plate (70) and the downwind plate (75).

The auxiliary protrusion (85) has an inverted V shape formed by making the fin (36) protrude. In the fin (36) of the present embodiment, each auxiliary protrusion (85) protrudes to the right when viewed from the leading edge (38) of the fin (36). The ridge (85 a) of the auxiliary protrusion (85) is substantially in parallel with the leading edge (38) of the fin (36). That is, the ridge (85 a) of the auxiliary protrusion (85) intersects with the airflow direction in the air passage (40). In addition, the lower end of the auxiliary protrusion (85) is tilted downward toward the downwind side.

As shown in FIG. 5(B), the height H5 of the auxiliary protrusion (85) in the protrusion direction is smaller than the heights H1, H2, H3 of the first to third protrusions (81, 82, 83) (H5<H1=H2=H3). As shown in FIG. 5(A), the width W5 of the auxiliary protrusion (85) in the air passage direction is smaller than the width W3 of the third protrusion (83) in the air passage direction (W5<W3).

The downwind plate (75) of the fin (36) is provided with a vertically extending water-conducting rib (49), a plurality of downwind tabs (48) arranged in the vertical direction, and a plurality of downwind protrusions (84) each provided between vertically adjacent downwind tabs (48).

The water-conducting rib (49) is an elongated recessed groove extending vertically along the trailing edge (39) of the fin (36). The water-conducting rib (49) extends from the upper end to the lower end of the downwind plate (75) of the fin (36).

Each of the downwind tabs (48) is a small rectangular piece formed by cutting and bending the fin (36). The downwind tabs (48) keep a space between the fins (36), with the tips thereof being in contact with their adjacent fin (36).

Each downwind protrusion (84) has an inverted V shape formed by making the downwind plate (75) protrude. In the fin (36) of the present embodiment, each downwind protrusion (84) protrudes to the right when viewed from the leading edge (38) of the fin (36). Ridges (84 a) of the downwind protrusions (84) are substantially in parallel with the leading edge (38) of the fin (36). That is, the ridges (84 a) of the downwind protrusions (84) intersect with the airflow direction in the air passage (40).

As shown in FIG. 5(B), the height H4 of the downwind protrusion (84) in the protrusion direction is equal to the heights H1, H2, H3 of the first to third protrusions (81, 82, 83) (H4=H1=H2=H3). As shown in FIG. 5(A), the width W4 of the downwind protrusion (84) in the air passage direction is equal to the width W2 of the second protrusion (82) in the air passage direction (W4=W2).

The fin (36) is provided with two horizontal ribs (91, 92), and the above-described first protrusion (81) which lie across the upwind plate (77) and the intermediate plate (70).

The first protrusion (81) comprises an intermediate heat-transfer portion provided at a middle portion, in the vertical direction, of the upwind plate (77). The first protrusion (81) comprises an upwind side heat-transfer portion which promotes heat transfer between the fin (36) and air on the upwind side of the intermediate plate (70).

In each fin (36), the upper horizontal rib (91) is provided at an area on the upper side of the first protrusion (81) and the upwind tab (95), and the lower horizontal rib (92) is provided at an area on the lower side of the first protrusion (81) and the upwind tab (95). The horizontal ribs (91, 92) are comprised of raised lines which protrude toward the air passage (40). The direction to which the horizontal ribs (91, 92) protrude is the same as the protrusion direction of the protrusions (81, 82, 83, 84). The upper horizontal rib (91) extends horizontally from the leading edge (38) of the fin (36) to an upper portion of the second protrusion (82). The lower horizontal rib (92) extends horizontally from the leading edge (38) of the fin (36) to a lower portion of the second protrusion (82). That is, in the fin (36), the two horizontal ribs (91, 92) extend linearly in the protruding direction of the upwind plates (77) (i.e., in the air passage direction). The horizontal ribs (91, 92) comprise reinforcing ribs which prevent the upwind plate (77) from being bent toward the air passage (40) with respect to the intermediate plate (70) of the fin (36). The horizontal ribs (91, 92) also comprise upwind side heat-transfer portions which promote heat transfer between the fin (36) and air on the upwind side of the intermediate plate (70).

The upwind tab (95) as a raised portion is provided on the front side of each of the upwind plates (77). The upwind tab (95) comprises an intermediate heat-transfer portion provided at a middle portion, in the vertical direction, of the upwind plate (77). The upwind tab (95) is a small rectangular piece formed by cutting and bending the fin (36) so as to protrude in a thickness direction of the fin (36). The front surface of the upwind tab (95) is tilted obliquely downward with respect to the air passage direction (i.e., the horizontal direction). Thus, an airflow resistance of the heat exchanger (30) can be reduced, compared to the case in which the front surface of the upwind tab (95) is vertical. The upwind tab (95) keeps a space between the fins (36), with the tips thereof being in contact with the adjacent fin (36). The upwind tab (95) also comprises an upwind side heat-transfer portion which promotes heat transfer between the fin (36) and air on the upwind side of the intermediate plate (70).

—Reduction of Frost Adhering on Surfaces of Fins—

As described above, the outdoor heat exchanger (23) of the present embodiment functions as an evaporator in the heating operation. In the heat exchanger (30) in the heating operation, the evaporation temperature of the refrigerant may sometimes be below 0° C., and frost may adhere to the surface of the fin (36). In the heat exchanger (30) of the present embodiment, the air before flowing into the air passage (40) is cooled/dehumidified by the upwind plates (77), thereby reducing the accumulation of frost on the inner side of the air passage (40).

Specifically, the air which has been transferred by the outdoor fan (15) and flowed into the heat exchanger (30) flows to the downwind side along each of the upwind plates (77). The air flowing on lateral sides of the upwind plates (77) contacts the upwind tab (95) and the first protrusion (81), and is cooled. The air which has flowed around the upwind tab (95) and the first protrusion (81) and moved to the upper side or the lower side of the upwind tab (95) and the first protrusion (81) contacts the horizontal ribs (91, 92), and is cooled. Thus, in the fin (36), the upwind tab (95), the first protrusion (81), and the horizontal ribs (91, 92) comprise heat-transfer promotion portions which promote heat transfer between air and the upwind plates (77).

When the air is cooled by the upwind plates (77) to a temperature equal to or lower than a dew point, moisture in the air is condensed. When the air is cooled by the upwind plates (77) to a temperature equal to or lower than 0° C., moisture in the air is frozen, and frost adheres to the surfaces of the upwind plates (77). Thus, on the lateral sides of the upwind plates (77), moisture in the air is condensed or turns into frost, thereby dehumidifying the air.

The air dehumidified on the lateral sides of the upwind plates (77) flows to the air passages (40) partitioned by the intermediate plates (70). The intermediate plates (70) are relatively close to the flat tubes (33), and thus, the air flowing in the air passages (40) is cooled rapidly. However, this air has been dehumidified before flowing into the air passages (40), and therefore, the accumulation of frost on the surfaces of the intermediate plates (70) is reduced.

Advantages of Embodiment

In the above embodiment, the upwind plates (77) extend from the intermediate plates (70) of the fin (36) toward the upwind side. Thus, the air before flowing into the air passages (40) can be cooled and dehumidified. Moreover, since each of the upwind plates (77) is provided with the upwind tab (95), the first protrusion (81), and the horizontal ribs (91, 92), it is possible to promote heat transfer between the air and the upwind plates (77), and improve the effect of dehumidifying the air. By dehumidifying the air before flowing into the air passages (40) in the manner as described above, the accumulation of frost on the surfaces of the intermediate plates (70) is reduced. As a result, it is possible to prevent a reduction in heat-transfer rate of the fin (36) and an increase in flow pass resistance of the air passages (40) due to accumulation of frost.

Since the accumulation of frost on the intermediate plates (70) is reduced as described above, it is possible to reduce the time of the above-mentioned defrosting operation. As a result, it is possible to extend the time of the heating operation, and promote energy conservation.

Further, the two horizontal ribs (91, 92) provided on each of the upwind plates (77) prevent the upwind plates (77) from being bent in the horizontal direction with respect to the intermediate plate (70). Such bending of the upwind plates (77) can be further prevented by the upwind tab (95) whose tip is brought into contact with the adjacent fin (36).

Other Embodiments

In the upwind plates (77) of the above embodiment, any of the upwind tab (95), the first protrusion (81), and the two horizontal ribs (91, 92) may be omitted. Further, each of the upwind plates (77) may be provided with the louvers (50 a, 50 b) of the above embodiment, and the louvers (50 a, 50 b) may be used as upwind side heat-transfer portions (raised portions).

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful for a heat exchanger having a flat tube and a fin, and configured to exchange heat between a fluid flowing in the flat tube and air.

DESCRIPTION OF REFERENCE CHARACTERS

-   -   10 air conditioner     -   20 refrigerant circuit     -   30 heat exchanger     -   33 flat tube     -   36 fin     -   38 leading edge     -   40 air passage     -   46 tube insertion portion     -   70 intermediate plate     -   75 downwind plate     -   77 upwind plate     -   81 first protrusion (upwind side heat-transfer portion,         intermediate heat-transfer portion)     -   91 upper horizontal rib (upwind side heat-transfer portion)     -   92 lower horizontal rib (upwind side heat-transfer portion)     -   95 upwind tab (upwind side heat-transfer portion, raised         portion, intermediate heat-transfer portion) 

1. A heat exchanger, comprising: a plurality of flat tubes arranged one above another such that flat surfaces thereof face each other; and a plurality of vertically extending, plate-like fins arranged in an extension direction of the flat tubes, wherein each of the fins includes a plurality of intermediate plates arranged one above another and dividing a space between adjacent ones of the flat tubes into air passages, a plurality of tube insertion portions each provided between vertically adjacent ones of the intermediate plates, with an upwind side thereof being open such that a corresponding one of the flat tubes is inserted therein, a vertically extending downwind plate that is continuous with downwind ends of the plurality of intermediate plates arranged one above another, and a plurality of upwind plates extending further toward an upwind side than the flat tubes from upwind side ends of the intermediate plates, and each of the upwind plates is provided with at least one upwind side heat-transfer portion which projects in a thickness direction of the fins.
 2. The heat exchanger of claim 1, wherein the upwind side heat-transfer portion includes a rib which extends in a protruding direction of the upwind plates.
 3. The heat exchanger of claim 2, wherein the upwind side heat-transfer portion includes an intermediate heat-transfer portion provided at a middle portion, in a vertical direction, of each of the upwind plates, and the rib provided on at least one of an upper side or a low side of the intermediate heat-transfer portion.
 4. The heat exchanger of claim 1, wherein the upwind side heat-transfer portion includes a protrusion which extends in a direction orthogonal to an air passage direction.
 5. The heat exchanger of claim 1, wherein the upwind side heat-transfer portion includes a raised portion formed by cutting and bending part of the fin.
 6. An air conditioner, comprising a refrigerant circuit including the heat exchanger of claim 1, wherein the refrigerant circuit performs a refrigeration cycle by circulating a refrigerant.
 7. The heat exchanger of claim 2, wherein the upwind side heat-transfer portion includes a protrusion which extends in a direction orthogonal to an air passage direction.
 8. The heat exchanger of claim 3, wherein the upwind side heat-transfer portion includes a protrusion which extends in a direction orthogonal to an air passage direction.
 9. The heat exchanger of claim 2, wherein the upwind side heat-transfer portion includes a raised portion formed by cutting and bending part of the fin.
 10. The heat exchanger of claim 3, wherein the upwind side heat-transfer portion includes a raised portion formed by cutting and bending part of the fin.
 11. The heat exchanger of claim 4, wherein the upwind side heat-transfer portion includes a raised portion formed by cutting and bending part of the fin.
 12. An air conditioner, comprising a refrigerant circuit including the heat exchanger of claim 2, wherein the refrigerant circuit performs a refrigeration cycle by circulating a refrigerant.
 13. An air conditioner, comprising a refrigerant circuit including the heat exchanger of claim 3, wherein the refrigerant circuit performs a refrigeration cycle by circulating a refrigerant.
 14. An air conditioner, comprising a refrigerant circuit including the heat exchanger of claim 4, wherein the refrigerant circuit performs a refrigeration cycle by circulating a refrigerant.
 15. An air conditioner, comprising a refrigerant circuit including the heat exchanger of claim 5, wherein the refrigerant circuit performs a refrigeration cycle by circulating a refrigerant. 